Electric switch



April 9, 1957 H. J. CROMWELL ETAL 2,788,414

ELECTRIC SWITCH Filed NOV. 18, 1954 11vVE1vT0R5 anon/as a. 5/10/27 m now .1. manual 7 [/11 Aime/W United States Patent ELECTRIC SWITCH Harold J. Cromwell and Brooks H. Short, Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich a corporation of Delaware Application November 18, 1954, Serial No. 469,788 Claims. (Cl. 200-113) This invention relates to electric switches and more particularly to a thermostatic type switch that is suitable for use with a vehicle signal circuit.

The present invention is directed to an improved switch that has all of the operable parts substantially vertically mounted on a base so that they may be enclosed by a cover. This switch further will provide a distinct and clearly audible sound when operating so as to advise the operator of the vehicle of the proper operation of the signal circuit.

It is an object of the present invention to provide a switch wherein all of the working parts of a switch are mounted on an insulated base and are enclosed in a cup-shaped cover. The parts carried by the insulated base include a U-shaped yoke which carries the fixed end of a substantially fiat slotted metal strip member so that the free end of the member may reciprocate between the arms of the yoke. The slotted member when formed has the outside portion between the slots shortened so that the central portion is under compression relative to the remaining portions of the member. This stressed portion will cause the member to move with a snap action that is accompanied by an audible sound when the member reciprocally moves a contact carried on the free end into engagement with a stationary contact carried by the base. The snap acting movement of the member occurs in response to a variation in tension which is applied through a bent arm or fulcrum that is carried near the fixed end of the member. This varition in tension is supplied by a thermoresponsive member or element which is substantially disposed in parallel and spaced from said member. The thermoresponsive member which elongates when heated in response to current passing therethrough has one end adjustably carried by the base and when cool has the other end secured under tension and disposed to pass over the fulcrum so that the bending movement applied through the fulcrum to the stressed portion of the member will cause the free end thereof to snap over the center line of the member and cause an engagement between the contacts. The elongation of the thermoresponsive member causes the stress on the central portion of the strip member to be relieved whereby the contact carried thereby is moved with a snap action out of engagement with said stationary contact. The movement between the contacts is caused by an intermittent flow of current therethrough as governed by the alternate lengthening and shortening of the thermoresponsive member.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings where in a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figure 1 is a view, partly in section, showing the arrangement of the parts of a switch according to the present invention.

Figure 2 is a view taken along line 2-2 in Figure l.

2,788,414 F atented Apr. 9, 1957 Figure 3 is a view taken along line 33 in Figure 1.

Figure 4 is a perspective view of the snap acting contact actuator as used in the switch in Figure 1.

Figure 5 is a view of a modified form of the switch according to the present invention.

In the drawings the numeral is used to designate a switch which is adapted to alternately make and break an electric circuit. The switch 20 is provided with a support 22 which may be formed of suitable insulating material which carries a U-shaped yoke member 24 that has a pair of substantially parallel arms 26 which are joined by an intermediate portion 28. The yoke member 24 has a pair of ears 30 which are formed thereon adjacent the intermediate portion 28 and asecond pair of ears 32 which are formed on the arms 26 at a spaced distance from the intermediate portion 28.

The switch is also provided with a snap acting member 34, most clearly seen in an unstressed condition in Figure 4, which has a pair of ears 36 which are secured to ears 36 when the end 38 is fixed relative to the yoke 24. The end 40 of member 34 is freely movable between the arms 26 of the yoke. The member 34 is formed of a unitary metal part with a pair of longitudinally extending slots 42 which divides the member into three. interconnected longitudinally extending portions. 'The center portion 44, as disposed between slots 42, is stressed relative to the outer portions 45 of member 34 by shortening the material of the outer portion 45. The material of the outer portions 45 of the strip is kinked as I at 46 which kink is located so as to engage the cars 32 when the end 33 is atfixed on the yoke 24. The free end 46 has a movable contact 48 suitably secured thereon which is adapted to engage a fixed contact 50 as carried on a contact arm 52 which extends from the insulated base 22. The contact 43 is normally out of engagement with the contact 50 when the various portions of the snap acting member 38 are in a normal position and stress is not applied thereto. When this normal position of member 34 occurs, one of the outer portions 45 will engage a stationary abutment as carried by yoke member 24. When member 34 is stressed out of its normal position, as will be hereinafter described, the end 40 will reciprocally move contact 48 into engagement with contact 59 with a clearly audible sound. The stressing of member 34 is accomplished by a fulcrum member 56 and a thermoresponsive element or wire 58. The fulcrum member 56 is formed of a unitary metal part and has one end 57 secured to the fixed end 33 of member 34 between the cars 36, and has an extending bent portion which provides an abutment which has an end 62 that engages the stressed central portion 44 at a point between the ears 3% and 32. Thus when stress is applied by wire 58 through the abutment 60 to the end 62 of fulcrum 56, the central portion 44 of member 34 will be moved in a direction toward the ears 32 while the outer portions 45 are held immovable by the cars 32. This relative movement will cause a reverse bend to be formed in center portion 44 and cause the end 40 to move with a snap action over the center line ofmeinber 34 and cause an engagement between contacts 48 and 5t).

The thermoresponsive element or wire 58 is of a material which will elongate when heated in response to current flow therethrough. The wire 58 has one end secured to an upstanding portion 63 of arm 64 which is suitably secured to base 22 and has its other end passing over the abutment 60 and secured to the end 57 of the fulcrum member 56. This element or wire 58 is tensioned when cool by bending the portion 63 of arm 64 in a counterclockwise direction as seen in Figure 2 so that a stress as heretofore described will cause member 34 to move contact 48 into engagement with contact 50.

This movement of the free end 40 from or to its normal position where it rests against abutment 54 into a position wherein contact 48 engages 50, is accompanied by a snap action which is accompanied by an audible clicking sound as the curvature of the stressed portion 44 is re versed.

When contact 50 is in engagement with the contact 43, current will flow through the thcrmoresponsive Wire 58 through a circuit which includes terminal member 66, which is integrally formed with the stationary contact carrying arm 52, contact 50, contact 48, the snap acting member 34, the fulcrum member 56, the thermoresponsive wire 58, and the bent arm 64 which is integrally formed with the terminalmember 68 as'carried by the support 22. When the current flows through contacts 43 and d, the thermoresponsive wire 58 will be heated and elongate. This elongation ofv wire 58 will lessen the tension of the fulcrum member 56 and thereby cause the stress applied on the center portion 44 of the member 34 through fulcrum 56 to be relieved. When this occurs the curvature of portion 44 reverses and the free end 40 reciprocates with a snap action in a direction to break the engagementbetween. contacts 48 and 5d and cause the circuit through wire '58 to be broken. The breaking of the circuit through wire 58 permits the wire to cool and contract and re-apply the tension through the fulcrum member 56 to cause the reengagement of the contacts 48 and 50. This breaking and making of the engagement between. the contacts occurs in a timed cycle that is spaced by a short predetermined time delay as effected by the heating and cooling of the thermoresponsive element or wire 58. 7

From the above it is apparent that if one of the terminals such as 68 is connected with the battery side of the circuit and the other terminal 66 is connected With the indicating end pilot lights of the turn signal circuit, thepilot light will flicker simultaneously with the indicating lights. in the embodiment as shown in Figure 5 wherein a switch A is shown and except where otherwise indicated, like reference numerals refer to like parts as heretofore described, the center terminal 70, which is connected with the thermoresponsive wire 82, is connected with the battery terminal, not shown. One of the outer terminals '72 is connected with the pilot light circuit and the other terminal 74 is connected with the indicating light signals. These terminals 72 and 74 are connected with stationary contacts 76 and 7%, respectively, that are disposed on opposite sides of the snap acting contact actuator 85 The contact actuator 86 is stressed when the thermoresponsive wire %2 is cold,

.so that it is in contact with the terminal '74 as associated with the headlight circuit. Thus a sufficient current will pass through wire 82 to cause it to be heated and elongate and relieve the stress on 86 so that engagement is made with the terminal 72 connected with the pilot circuit. The current requirements of the pilot lamp are sufficiently small so that the member 82 cools, in spite of the limited amount of current passing therethrough, and contracts to re-apply the tension on member 8% and cause the engagement with the contact 78.

It is clearly apparent that the action of the fulcrum 56 on'the member 34 may be reversed if desired. While this is not shown in the drawings, it is clear that if the fulcrum 56 is provided with a bifurcated end, it could be so constructed so as to engage the outer portions 45 of the snap acting member 34. In this embodiment a' fixed abutment is disposed:- relative to the member 34 so as to engage the stressed center portion 44. If this construction is utilized, the snap action occurs when the outer portions of member 34 are forced out of their normal position by the bifurcated end of the fulcrum member 56.

'The-switchac'c'ording to the present invention has all of its parts arranged substantially in parallel relation to provide a very compact switch structure that may be received in a cover 84 which is secured to base 22. It is also manifest that the adjustment of the time cycle of operation of the switch may be varied as the tension on the thermoresponsive member is charged as when the bent portion 63 of arm 64 is moved either in a clockwise or counterclockwise direction. A further adjustment is provided for the switch 20 when the extending arm 52 of the stationary contact is bent so that the spacing between contact Stl and 48 is varied. These adjustments can be made Without diificulty to obtain the proper switch operation. Timing can also be varied by bending arms 32.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In an electric switch, the combination comprising; an insulated support, a second support carried by said first support, a fixed contact carried by said first support, a snap acting contact actuator comprising a single strip of metal having one end attached to said second support and a second end freely movable and normally spaced from said fixed contact, a fulcrum carried by said actuator positioned between the fixed and free ends thereof, and a thermoresponsive element having one end adjustably carried by said support and the other end passing over said fulcrum and attached to the fixed end of said actuator, and tensioned when cool for biasing said actuator into mating engagement with said fixed contact, said element being adapted in response to current flowing therethrough when said actuator and contact are in engage ment for elongating and releasing the tension in said actuator for causing the actuator to return to its normal position with a snap action for breaking said mating engagement.

2. A device of the character described comprising; an insulated support, a U-shaped yoke having a midportion and a pair of arms which are attached to said support, a snap acting spring member comprising a single strip of metal having one end fixed to the midportion of said U-shapcd yoke and a free end movable between the arms of said yoke, an abutment means carried on the arms of said yoke in engagement with said spring member between said fixed and free ends, a fulcrum carried by said spring member disposed between said abutment means and said fixed end, a stationary contact carried by said support and normally spaced from said spring member, when said spring member is unstressed, and a thermoresponsive member having one end fixed to said support and disposed substantially in parallel relative to said spring member with the other end operatively connected with said fulcrum, said thermoresponsive member being tensioned when cold to stress said spring member into contact with said contact for completing a circuit therebetween and adapted when heated in response to current passing therethrough to elongate and relieve the stress on said member whereby said member moves from engagement with said contact with a snap action.

3. A device of the character described comprising; a U-shaped yoke having a pair of spaced arms and a mid-portion, a snap acting member having one end secured to said mid-portion and another end freely movable between said arms, said member being formed of a unitary metal piece with a pair of longitudinally extending slots defining a center portion interconnected at its ends with the other portions of said member surrounding said slots', said center portion being stressed relative to outer portions of said member by lengthening predetermined portions of the material of said strip surrounding said slots, a stationary abutment means carried by said yoke disposed to contact portions of said member between said fixed and free ends, a movable abutment having an end disposed to engage said member between the fixed end and the stationary abutment,

and a thermoresponsive means having one end fixed relative to said yoke and disposed substantially parallel to and spaced from said member with the other end operatively connected with said movable abutment whereby said means when cold is tensioned to move said movable abutment relative to said fixed abutment for stressing said member and cause the free end thereof to move with a snap action into engagement with a stationary contact and when heated in response to a current flow passing between said contact and said members to elongate and permit said movable abutment to move relative to said fixed abutment and relieve the stress applied on said member for causing said member to move with a snap action out of engagement with said contact.

4. A switch of the character described comprising; a support, a snap acting member comprising a single metal strip having one end fixed on said support and the other end freely movable, a stationary contact normally spaced from the free end of said member, a pair of abutments longitudinally spaced between the ends of said member with one of said abutments being carried by said member and the other abutment carried by said support, a thermoresponsive means having one end fixed relative to said support and the other end operatively associated with one of said abutments, said means being disposed substantially in parallel to said member and under a predetermined tension when cold for moving the abutment associated therewith in one direction relative to the other abutment whereby said member is stressed and the free end thereof moves with a snap action into engagement with said contact, said means being adapted to elongate when heated in response to current passing therethrough and relieve said tension whereby the direction of movement between said abutments is reversed and the stress on said member is relieved and the free end thereof moves with a snap action for breaking the engagement with said contact.

5. A device of the character described, comprising; an insulated support, a U-shaped yoke carried by the support having; a pair of arms, an intermediate portion joining said arms and a pair of ears formed on said arms disposed adjacent the intermediate portion, a snap acting member having one end fixed to said ears and the other end freely movable between the arms of said yoke, a stationary contact carried by said support out of engagement with a contact carried by the free end of said member when said member is unstressed and is in engagement with a stop spaced from said stationary Contact, a second pair of ears carried by the arms of said U-shaped yoke spaced between said first pair of ears and said support and adapted to abut one side of said member, a bent arm having; one end secured to the tired end of said member intermediate said first pair of ears, a bent portion and another end in contact with a surface portion on the other side of said member intermediate the first and second pairs of ears, and a thermoresponsive element having one end adjustably secured to said support and the other end passing over the bent portion of said arm, said element being adjusted when cold to be under tension for pressing the other end of said arm against said member whereby the free end of said member moves with a snap action which is accompanied by an audible sound so that the contact carried thereon is moved into mating engagement with the stationary contact, said element being adapted when heated by a current passing between said contacts to elongate for relieving the tension on said arm and stress on said member whereby the contact carried thereon is moved with a snap action out of engagement with said stationary contact and said member engages said stop with an audible sound, the movement of said contact into and from engagement with the stationary contact occurring in a timed cycle and being spaced by a short predetermined time delay as effected by the heating and cooling of said element.

References Cited in the file of this patent UNITED STATES PATENTS 

